[Map] Emerald available size

Hi all, returning after a couple of months out.

After lots of thinking and planning I left my ROM hacking project to be lost among all of those ideas that are great at first, but afterwards you don't know what to do with them.
A week ago I decided to revisit it and try to make the hack by myself from the ground up. So, I've been researching to find which could be the best base to start with, but given the scope of my project (Kanto, Orange Islands, Johto and Hoenn + BF), I wanted to to be sure it could be done before getting my hands dirty.
To the point then, does Emerald/Ruby have enough space for me to put 3.5 regions and, let's say, 450 pokémon? It's the only thing that stops me from start hacking right away.

Thanks in advance!

You could try to expand the rom and add the Pokémon with the PGE, it does it all and a little more, it can help you. (Sorry for the english)

Thanks! Will try that!